Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Difference of Electron Capture and Transfer Dissociation Mass Spectrometry on Ni<Superscript>2+</Superscript>-, Cu<Superscript>2+</Superscript>-, and Zn<Superscript>2+</Superscript>-Polyhistidine Complexes in the Absence of Remote Protons

Electron capture dissociation (ECD) and electron transfer dissociation (ETD) in metal-peptide complexes are dependent on the metal cation in the complex. The divalent transition metals Ni²⁺, Cu²⁺, and Zn²⁺ were used as charge carriers to produce metal-polyhistidine complexes in the absence of remote protons, since these metal cations strongly bind to neutral histidine residues in peptides. In the case of the ECD and ETD of Cu²⁺-polyhistidine complexes, the metal cation in the complex was reduced and the recombination energy was redistributed throughout the peptide to lead a zwitterionic peptide form having a protonated histidine residue and a deprotonated amide nitrogen. The zwitterion then underwent peptide bond cleavage, producing a and b fragment ions. In contrast, ECD and ETD induced different fragmentation processes in Zn²⁺-polyhistidine complexes. Although the N–C_α bond in the Zn²⁺-polyhistidine complex was cleaved by ETD, ECD of Zn²⁺-polyhistidine induced peptide bond cleavage accompanied with hydrogen atom release. The different fragmentation modes by ECD and ETD originated from the different electronic states of the charge-reduced complexes resulting from these processes. The details of the fragmentation processes were investigated by density functional theory.

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Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Specific features of absorption of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, and Pb<Superscript>2+</Superscript> cations from aqueous solutions by calcium phosphates

Kinetic characteristics of the interaction of trisubstituted calcium phosphate Ca₃(PO₄)₂ · xH₂O with Cu²⁺, Zn²⁺, Co²⁺, and Pb²⁺ ions in aqueous solutions were studied.     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Extraction of Cu<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, and Co<Superscript>2+</Superscript> ions from aqueous solutions with calcium and magnesium phosphates

The efficiency of calcium and magnesium phosphates of different compositions in the extraction of Cu²⁺, Zn², and Co²⁺ ions from aqueous solutions was studied.     

Vinylimidazole copolymers: coordination chemistry,solubility, and cross-linking as function of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> complexation

P(1-VIm-co-MMA) copolymers with 4 or 44 wt.% 1-VIm (abbreviated PVM-4 and PVM-44) where polymerized from 1-VIm (1-vinylimidazole) and methylmethacrylate with azobisisobutyronitrile as initiator and reacted with either Cu²⁺ or Zn²⁺. The resulting coordinated polymer complexes were studied using ICP-AES, CP/MAS ¹³C NMR, conductivity measurements, vibrational spectroscopy (mid-FTIR and far-FTIR), DSC, and EPR. It was established by ICP-AES, CP/MAS ¹³C NMR, conductivity, mid-FTIR and EPR measurements that the transition metal ions in the complexes were exclusively coordinated by the imidazole ligand. The coordination geometry is square planar with regard to Cu(II) complexes. The strong interaction between the polymeric imidazole ligand and the transition metal ion cross-links the system, resulting in augmentation of T _g (the glass transition temperature), especially for copolymers with high relative amount of 1-VIm. The effect of changing metal ion is more complicated and depends on both the strength of the coordinate interaction as well as the coordination number. The solubility of the coordinate polymer complex in conventional solvents is low due to the coordinate cross-links. However, the coordinate polymer complexes are soluble in strongly coordinating solvents such as acetonitrile and dimethylsulfoxide.     

Thermodynamic behavior of complexation of 18-crown-6 with Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Zn<Superscript>2+</Superscript> metal cations in methanol-water binary media

The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl⁺, Pb²⁺, Hg²⁺, and Zn²⁺ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H₂O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg²⁺ and Zn²⁺ cations, but in the case of Tl⁺ and Pb²⁺ cations, in addition to 1:1 stoichiometry, 1:2 (ML₂) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH _c⁰ and ΔS _c⁰), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K _f ) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent. The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations change with the nature and even with the composition of the mixed solvent. The article was submitted by the authors in English.     

Thermodynamic characteristics of formation reactions of Zn<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript> complexes with succinic acid in aqueous solutions

The heat effects of complex formation between zinc(II) and nickel(II) ions and succinic acid were determined calorimetrically at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Solvothermal Syntheses,Crystal Structures,and Properties of New [Mn(<Emphasis Type="BoldItalic">dien</Emphasis>)<Subscript>2</Subscript>]<Superscript>2+</Superscript> Complexes

Summary.  The two new compounds Mn(dien)₂[MoS₄] (1) and Mn(dien)₂[Mo₂O₂S₆] (2) (dien = diethylenetriamine) were prepared under solvothermal conditions. Both compounds were obtained as phase-pure products. The structures consist of new [Mn(dien)₂]²⁺ cations and isolated tetrahedral [MoS₄]²⁻ (1) or [Mo₂O₂S₆]²⁻ (2) anions. Between the anions and the cations, hydrogen bonding is observed. Compound 1 crystallizes in the tetragonal space group I (a = 10.219(2), c = 9.259(2) ?, Z = 2), whereas 2 crystallizes in the monoclinic space group P2₁/c (a = 8.703(2), b = 18.390(4), c = 14.603(3) ?, β = 103.18(3)°, Z = 4). The thermal behaviour of the thiomolybdates was investigated using difference thermoanalysis (DTA) and thermogravimetry (TG). Both compounds decompose under argon with a single endothermic signal in the DTA curve (peak maximum: 252 (1) and 242°C (2)). Received November 5, 2001. Accepted December 27, 2001     

Crystal structures of a family of layered coordination polymers containing divalent metal ions (Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) and the 3-amino 4-methyl benzoate ion

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans-MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in μ³-N,O,O′ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N–H?O and C–H?O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P2₁/c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, β = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R(F) = 0.026, wR(F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P2₁/c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, β = 95.473(4)°, V = 703.65(12) ų, Z = 2, R(F) = 0.041, wR(F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P2₁/c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, β = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R(F) = 0.028, wR(F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P2₁/c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, β = 95.941(3)°, V = 694.89(7) ų, Z = 2, R(F) = 0.038, wR(F ²) = 0.107.     

Synthesis and Characterization of New Os<Subscript>2</Subscript><Superscript>5+</Superscript> and Os<Subscript>2</Subscript><Superscript>6+</Superscript> Azido Complexes

Reaction of Os₂(OAc)₄Cl₂ with an excess of HDPhF (HDPhF = N,N′-diphenylformamidine) gives a high yield of Os₂(DPhF)₄Cl₂ (1), which can be converted to its azido analog, Os₂(DPhF)₄(N₃)₂ (3), by treatment with NaN₃. We report a major improvement on the preparation of Os₂(chp)₄Cl (2; Hchp = 2-chloro-6-hydroxypyridine) by synthesizing the compound in the reducing solvent ethanol. Reaction of 2 with NaN₃ affords the azido complex Os₂(chp)₄N₃ (4). Compound 3 has been examined by X-ray crystallography, and has an Os–Os bond distance of 2.45 Å, suggesting a (π*)² ground state for the molecule.     

Zn<Superscript>2+</Superscript> cation triggers self-assembly of cyclen into a stable metallogel

A novel type of ligands contained 1,4,7,10-tetrazacyclododecane and functionalized by two azobenzene moieties grafted with two alkyl chains was designed and synthesized. The ligands with long alkyl chains can form metallogels in the presence of Zn²⁺ cations. The formation of metallogel was followed by NMR and electronic spectral detection. The morphology of the xerogels is varied with the equivalent of Zn²⁺ cations and the concentration of the gel. Spectral and structural analysis indicated that the driving forces of the gel formation were attributed to intermolecular hydrophobic interactions between alkyl chains and π-π interaction between azobenzenes.     

Selective extraction of Fe<Superscript>3+</Superscript> ions from Fe<Superscript>3+</Superscript>-Zn<Superscript>2+</Superscript> mixture with phosphate sorbents

The absorption of Fe³⁺ ions from Fe³⁺-Zn²⁺ mixture with zinc and calcium phosphates was studied.     

Syntheses,Crystal Structures,and Properties of Two <Emphasis Type="Italic">d</Emphasis><Superscript>10</Superscript> Metal Complexes Based on Ferrocenyl Ligands Bearing Pyrazolyl Pyridine Substituents

Two new complexes, namely, [Cd₂(L¹)₂(NCS)₄(DMF)₂] · 4H₂O (I) and {[Zn₃(L²)₄(SO₄)₃(H₂O)₈] · 3DMF · 6H₂O} _n (II) have been synthesized through self-assembly of Cd(II) or Zn(II) salts with ferrocenyl ligands bearing pyrazolyl pyridine substituents. The two compounds were characterized by IR spectra, element analysis, X-ray powder diffraction, single-crystal X-ray diffraction (СIF files CCDC nos. 949526 (I), 949527 (II)), and thermogravimetric analysis. Complex I crystallizes in the monocline space group P21/c and exhibits a discrete dinuclear structure. The adjacent dinuclear molecules are packed into a 1D linear chain through the hydrogen-bond interactions. Complex II is a neutral one-dimensional infinite zigzag coordination chain. The 3D packing diagram of II contains two types of voids and the solvated DMF and water molecules filled them and stabilized by the hydrogen bonds. In addition, the redox properties of both complexes I and II have also been investigated.     

两个双核稀土金属配位聚合物的溶剂热合成、晶体结构及荧光性质

以顺丁烯二酰肼（MH）为配体,通过溶剂热法合成了配位聚合物[Dy₂（MH）₆]_n·0.5DMF（1）和[Eu₂（MH）₆]_n（2）。通过红外光谱、X射线粉末衍射、X射线单晶衍射表征了2个晶体的结构。配合物1和2都是三斜晶系,P1空间群。以双核结构为顶点作图得到配合物的空间拓扑结构,拓扑类型为tsi。配合物的热重分析结果表明2个配合物在315℃左右仍有较好的热稳定性。固体荧光结果表明配合物2在激发波长为375 nm时有对应Eu³⁺的⁵D₀→⁷F_J（J=0~4）能级能量的5个发射峰,最强发射峰波长为616 nm,归属为Eu³⁺的⁵D₀→⁷F₂能级跃迁。     

两个双核稀土金属配位聚合物的溶剂热合成、晶体结构及荧光性质

以顺丁烯二酰肼(MH)为配体,通过溶剂热法合成了配位聚合物[Dy2(MH)6]n·0.5DMF(1)和[Eu2(MH)6]n(2)。通过红外光谱、X射线粉末衍射、X射线单晶衍射表征了2个晶体的结构。配合物1和2都是三斜晶系,P1空间群。以双核结构为顶点作图得到配合物的空间拓扑结构,拓扑类型为tsi。配合物的热重分析结果表明2个配合物在315℃左右仍有较好的热稳定性。固体荧光结果表明配合物2在激发波长为375 nm时有对应Eu~(3+)的5D0→7FJ(J=0~4)能级能量的5个发射峰,最强发射峰波长为616 nm,归属为Eu~(3+)的5D0→7F2能级跃迁。     

Characterization of extraframework Zn<Superscript>2+</Superscript> cationic sites in silicalite-2: a computational study

Siting and coordination of Zn²⁺ ions at six plausible positions in all-silicate ZSM-11 material known as silicalite-2 have been investigated via hybrid density functional theory method at the B3LYP level employing molecular cluster models to represent the active site. The symmetrical trapping of Zn²⁺ ions in six-membered ring (6MR) sites of the main channels with a fivefold coordination to the framework oxygens was associated with the most stable binding among the investigated sites. On the contrary, the cation was found to be most weakly bound in sites at the intersections where it was twofold coordinated with slightly shorter Zn–O distances. A basket-like position for Zn doping was also recognized that exhibited no clear trends in the electronic and structural properties investigated.